In connection with so-called jump-lifts, the elevator hoistway is taken into use already before the full length of the elevator hoistway has been completed. The top part of the elevator hoistway is constructed at the same time as an elevator car moving in the already completed bottom part of the elevator hoistway serves people on the lower floors of the building. In jump-lifts, the elevator car moving in the bottom part of the elevator hoistway is supported and moved during the construction-time use suspended on hoisting ropes that are supported by a supporting platform in the elevator hoistway, which ropes are moved with a hoisting machine that is usually supported on the supporting platform. Installation work is done in the parts of the elevator hoistway above this supporting platform. When the part of the elevator hoistway under construction above the supporting platform has reached a sufficient stage of completion, the completed part of the elevator hoistway can be taken into use. In this case a jump-lift is performed, wherein the supporting platform is lifted to a higher position in the elevator hoistway, thus extending the operating area of the elevator car upwards. A worksite crane in use in the construction of the building can, for example, be used for the lifting. Alternatively it has been possible to move the machine room platform that is being supported in the lifting on a support structure in the hoistway above the machine room platform. When the elevator hoistway has reached its final height, the machine room platform has usually been removed from the elevator hoistway and the final hoisting machine of the elevator has been brought into a machine room built at the end of the elevator hoistway. As a conclusion to the installation method the construction-time roping is removed and the elevator is reeved again with the final roping. Elevator rope technology that has been established for a long time has been used in jump-lifts. Thus, conventional spiral metal ropes, i.e. ropes with a longitudinal power transmission capability based essentially on metal fibers, have been used as construction-time ropes. These metal ropes are cheap in price and perform their construction-time tasks well, being simple and durable in their fixings, and they withstand worksite conditions without problems. The replacement of ropes that have served for a short while with new ropes as a conclusion to the method has been economical because metal ropes are inexpensive.
A problem in prior-art solutions has been that the hoisting arrangements needed for lifting the supporting platform take up a lot of space, are complex and are not sufficiently quick to use. More particularly the support points needed for moving and positioning the machine room platform are difficult to arrange. It would not be desirable to separately arrange numerous support points in a building. It has been noticed that the difficulty of finding support points that are sufficiently stable and durable effectively limits the maximum height to which a jump-lift can, with a reasonable work input, reach. A worksite crane must sometimes be used for moving the machine room platform, because the aforementioned problems make other solutions so awkward. Another problem has been, generally speaking, the demanding installation environment, which has set numerous practical challenges, which are connected to the smooth-running and safety of the installation and to the durability of structures. These are, inter alia, the space usage and complexity of the hoisting arrangement of the machine room platform, the center of mass and stability of the machine room platform during the lifting and while being in position, the center of mass and stability of the support arrangement to be used for the lifting during the lifting and while being in position, the setting of the support locking mechanism producing a suitable balance, the cramped layout of the machine room platform, suitable hoisting devices, the dimensioning of the hoisting machine for the final travel height, routing of the ropes with adequate run clearances, correct fitting of the rope length, the need for safe and spacious working space. These numerous variables that must be taken into account affect each other directly or indirectly and their overall effect is that the structure easily becomes complex and robust, and requires a lot of space.